1. Field of the Invention
The present invention relates to an image processing system which is capable of synthetically processing different types of data, such as image data as electrically read, code data as prepared by a personal computer, and bit map data as developed by an outline font, and more particularly to an image processing system which enables the editing of electronic images.
2. Discussion of the Related Art
FIG. 6 is a block diagram of a conventional digital image processing system. In a digital copying machine, an image input terminal (IIT) 43 reads an image of an original document by using a CCD line sensor, and converts an analog video signal as received into a digital signal. An image processing system (IPS) unit that executes correction, editing, and the like, converts the corrected signal into a two-level signal. An image output terminal (IOT) 46 produces a halftone image as a colligation of mesh-dots by controlling the turning on and off of pixels according to the two-level data.
Attempts have been made to couple the copying machine of this type with external devices, such as personal computers (PCs) and facsimile machines (FAX), and the IOT 46 is commonly used for those external devices. To this end, a selector 45 is provided between the IOT 46 and the IIT 43, as shown in FIG. 6. The selector 45 selectively couples the PC 41, FAX 44, and the IIT 43 with the IOT 44. With this arrangement, the image processing system produces a reproduced image or copy irrespective of the type of the input image data, such as the two-level data from the external devices, e.g., the PC 41 and the FAX 44, and the gradation data from the IIT 43. Since the data output from the PC usually takes the form of code data, the system converts the code data into bit map data, and then transfers the bit map data to the IOT 46. The data from the FAX 44 likewise is decoded and transferred to the IOT 46.
In the digital copying machine of this type, the copying machine and the external devices are functionally isolated from one another. The image forming and outputting operation of the system is ineffective.
To solve the problem, there has been developed a digital copying machine with an electronic RDH (recirculating document handler). In the copying machine, facsimile machine, and printer, there is a need for an electronic RDH for their post processing.
In the conventional RDH, a set of original documents is repeatedly read by an automatic image reader, and a requested number of copies of the set of documents is produced. Therefore, when the requested number of copies is increased, the number of times the document is handled is increased, thus, increasing the likelihood that the documents will be damaged. An electronic RDH can produce the requested number of copies while reading the documents only one time. In the electronic RDH, a data storage unit is provided for storing the image data. The memory capacity of the storage unit is desirably large. For this reason, a magnetic memory device, such as a hard disk, is used. Of course, a semiconductor memory may also be used. To output a requested number of copies, a set of original documents is read one time in the presented order, and the image data is stored into the storage unit. The image data stored is repeatedly read out of the storage unit in the presented order, and transferred to the image output terminal The image output terminal produces the requested number of copies.
Since the image data contains a tremendous amount of information, the memory capacity of the storage unit must be extremely large in order to store all of the image information of a plurality of original documents. To cope with this, the combination of a compressor and a decompressor is used to compress the data and to decompress the compressed data back into its original form. The compressor compresses the data to reduce the amount of image data that must be stored into the storage unit. The image data is read out of the storage unit and decompressed into its original form. The decompressed data is then transferred to the image output terminal.
In a magnetic memory device, such as a hard disk, an access time including a seek time and the like is approximately 1 M byte/sec. A normal signal transfer time is 10 M bytes/sec. Thus, a speed gap exists between the access time and the transfer time. To cope with the speed gap, a page buffer is provided. The compressed data from the compressor is temporarily stored in the page buffer. After the storage of the image data into the hard disk is completed, the data is read out of the hard disk into the page buffer. Then, it is input to the decompressor. The decompressed image data is then transferred to the image output terminal.
Editing commands, such as "cut and paste", masking, and "pickup and move", are difficult for the RDH to handle. The image data is read by the image reader, input to the control unit of the image processing system in real time and stored in a data storage unit. Therefore, the image data must be read out of the storage unit to be edited. Since the stored data is compressed data, positional information in a coordinate system cannot be obtained. The same is true for image data rotation. For this reason, to perform editing, the compressed data must be read out of a storage unit and decompressed. The decompressed data is developed into bit map data, and loaded into a page buffer. To this end, a page buffer for editing must be additionally provided. This leads to an increase in the cost of manufacturing.